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Measure epoch of timestamp-without-time-zone from local not UTC midni…

…ght.

This patch reverts commit 191ef2b
and thereby restores the pre-7.3 behavior of EXTRACT(EPOCH FROM
timestamp-without-tz).  Per discussion, the more recent behavior was
misguided on a couple of grounds: it makes it hard to get a
non-timezone-aware epoch value for a timestamp, and it makes this one
case dependent on the value of the timezone GUC, which is incompatible
with having timestamp_part() labeled as immutable.

The other behavior is still available (in all releases) by explicitly
casting the timestamp to timestamp with time zone before applying EXTRACT.

This will need to be called out as an incompatible change in the 9.2
release notes.  Although having mutable behavior in a function marked
immutable is clearly a bug, we're not going to back-patch such a change.
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1 parent 442da68 commit 0d9819f7e3be3c4186f0398d007d2fef8809da6a @tglsfdc tglsfdc committed Apr 10, 2012
Showing with 6 additions and 23 deletions.
  1. +3 −1 doc/src/sgml/func.sgml
  2. +3 −22 src/backend/utils/adt/timestamp.c
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@@ -6684,8 +6684,10 @@ SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40');
<term><literal>epoch</literal></term>
<listitem>
<para>
- For <type>date</type> and <type>timestamp</type> values, the
+ For <type>timestamp with time zone</type> values, the
number of seconds since 1970-01-01 00:00:00 UTC (can be negative);
+ for <type>date</type> and <type>timestamp</type> values, the
+ number of seconds since 1970-01-01 00:00:00 local time;
for <type>interval</type> values, the total number
of seconds in the interval
</para>
@@ -4066,32 +4066,13 @@ timestamp_part(PG_FUNCTION_ARGS)
switch (val)
{
case DTK_EPOCH:
- {
- int tz;
- TimestampTz timestamptz;
-
- /*
- * convert to timestamptz to produce consistent results
- */
- if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
- ereport(ERROR,
- (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
- errmsg("timestamp out of range")));
-
- tz = DetermineTimeZoneOffset(tm, session_timezone);
-
- if (tm2timestamp(tm, fsec, &tz, &timestamptz) != 0)
- ereport(ERROR,
- (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
- errmsg("timestamp out of range")));
-
#ifdef HAVE_INT64_TIMESTAMP
- result = (timestamptz - SetEpochTimestamp()) / 1000000.0;
+ result = (timestamp - SetEpochTimestamp()) / 1000000.0;
#else
- result = timestamptz - SetEpochTimestamp();
+ result = timestamp - SetEpochTimestamp();
#endif
break;
- }
+
case DTK_DOW:
case DTK_ISODOW:
if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)

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